The Effects of Shift Work on Circadian Rhythms, Sleep, and Diabetes

Understanding how shift work affects sleep, insulin, and diabetes

For about 20 million Americans, work is not nine-to-five but instead consists of shift work. This could be a second shift (from four to midnight), a third shift (from midnight to eight a.m.), or a split or swing shift that changes every two weeks. 

This unnatural schedule presents a significant challenge for our brain and autonomic system. They have evolved to function with day/night cycles dictated by the planet and cosmos, not an employer. This article will dive into that issue and illustrate some of the ways that shift work poses a significant health challenge. 

Circadian Rhythms

Our bodies have a constant rhythm of hormones and brainwaves triggered by day and night cycles. Shift work directly impacts these rhythms, with direct effects trickling down and influencing the other issues discussed later. 

Our brain and body produce hormones that help us be awake or asleep sometimes throughout the day or night. These hormones cause changes in the frequency at which our brains operate, producing a mental and physical effect that we perceive as alert or sleepy. 

The spectrum of light we’re exposed to, and the timing play a big part in this effect. It’s easy to see how it works by considering the physical world outside. Humans have lived outdoors for almost all of our million-plus-year history, exposed to the wavelengths of light at dawn, midday, and dusk. 

The light spectrum in the middle of the day has more blue wavelengths, while in the evening, the sunset provides longer wavelengths of a red hue. These trigger different neurohormones, such as cortisol or melatonin, and brainwave changes that make us alert or sleepy. 

When you work a shift, you’re fighting your circadian rhythms, trying to be awake when the environmental cues are telling your body to sleep, and vice versa. From the beginning, this is asking your body and brain to do something they weren’t built for. 

Before our modern lifestyle, one of the only reasons anyone would have stayed up all night was to keep an eye out for something dangerous; a "night watch." The night watch is inherently stressful, so your system reacts to your night work with a stress response. Your cortisol and adrenaline levels and blood pressure could be elevated. 

Research into circadian rhythms has found that partial adaptations happen over time, requiring at least one week. This is the exact interval used almost universally in swing shifts, so your schedule changes as your system is getting adapted! 

Effects on Diabetes

Shift work causes shifts in your hormone balance and autonomic stress responses, which put you at an increased risk of diabetes. 

Insulin Resistance

Elevated cortisol levels, and the chronic inflammation it causes, make you more prone to insulin resistance. When the body’s cells are inflamed, they don’t respond to insulin as effectively. In addition, cortisol causes your liver to release more glucose, so chronically elevated cortisol levels equal elevated glucose.

Glucose Metabolism

Research has shown that working night shifts or swing shifts disturbed the beta cell function in the pancreas, resulting in elevated blood glucose levels and blood sugar instability. These changes are the building blocks of type 2 diabetes.

Reduced Quality of Sleep

Reduced sleep quality is almost certain during shift work, partly because of the light spectrum issue and because everyone else is awake and probably not silent. Poor sleep quality is associated with an increased risk of impaired glucose tolerance, insulin resistance, and diabetes. 

Sleep Deprivation

Most shift workers still have two days of the week off from work, typically weekends. Usually, this schedule also results in staying awake during the daytime on the weekend, which means being sleep deprived once every week, from Sunday morning through Monday morning. 

Sleep deprivation also destabilizes blood sugar and insulin resistance, promoting metabolic disease. The rise in stress hormones has other detrimental effects secondary to chronic inflammation. 

Alcohol Consumption

Studies of shiftwork have confirmed that binge drinking is far more common in those who work shifts. This pathological consumption pattern can be self-medication for sleep problems or the elevated stress level that working shifts cause. Many demographics are at risk, with nurses over 50 identified as a particular affected risk group.

Poor Diet

Shift workers tend to eat at irregular intervals and times, with more tendency to skip meals at some times and overeat at other times. This can result in poor digestion and difficulty with overeating. The body responds better to eating on a regular schedule. 

The dysregulated eating schedule and poor food choices (in a search for convenience), mean shift workers are at risk of more problems. 

Shift Work Raises Risks

Working a shift schedule raises the risks of chronic inflammation, blood sugar instability, and type 2 diabetes, as well as increased alcohol consumption. Being awake during the night is not something your brain and physiology evolved to do. The body can adapt to a limited degree, but swing shifts prevent that adaptation. 

If a dayshift is available these additional health challenges could be eliminated. Sometimes that may not be an option, however. Additional measures can be taken if work provides no other scheduling options, so take a moment to read this article in your Revero app.